Elven are not adversely affected by bacteria, nor by most virii. A retrovirus that causes genetic disorders would be the main exception. Elven with hair below the neck, warts or raised moles have such a disorder, and are soon to die. Regular moles and freckles are harmless These retrovirii and some fungi are the only communicable disorders in the'elven.
The primary "sicknesses" stem from injuries, poisons, toxins, and various disruptions of bodily functions, such as those caused by overuse of magic, phystical strain, age, strong emotions, and sea travel. Curses can also cause an elven to be "sick".
Mental illness is common among elven, especially snow elven. Some common types are incorrect perception of reality, paranoia, rage, personifying objects, etc. Despite the fact that some result in violence, most forms of mental illness present in the population are merely "quirky", such as believing in imaginary friends. In addition, some religions are seen by others as being mass delusions. For snow elven in particular, knowledge magic causes contention because two different elven may receive two different versions of the truth from their magic. Is one insane, or just a lousy magician?
Dead elven are primarily decomposed by plants, insects, and fungi. A body that is kept safe from these things will eventually succomb to bacterial decomposition, but this process is considerably slower. Cave elven medicine includes ointments that prevent all decomposition, though the body is still subject to violent injury. The ointment has no effect on living tissue, and is even edible. The ointment is used to keep meat from spoiling.
Theoretically the magic that allows cave elven witches to speak to dead spirits and animate corpses as zombies would allow them to raise the dead, however this would require a great deal of magic, and a relatively "healthy" corpse.